A. Field of the Invention
The present invention relates to an apparatus, such as a lighting fixture, for diffusing light and for passing air through the fixture for cleaning it. Preferably, the fixture is used in public vehicles, such as subway or rail cars.
B. Description of the Related Art
Traditionally, lighting fixtures in public vehicles such as rail or subway cars have had sealed plastic lens covers, whose effectiveness as a seal against the collection of dirt is questionable because of the breathing action of the fixtures which is induced by temperature and pressure changes. Fixtures cannot as a practical matter be hermetically sealed; hence, films collect on the inside surfaces which become unsightly when illuminated. It has therefore become desirable to continuously clean the fixtures so as to avoid accumulation of films, dust, or other particulate matter.
A lighting fixture which sucks air through the fixture for cleaning out dust particles and the like is known from U.S. Pat. Nos. 4,352,323; 4,499,815; 4,907,142, 5,038,256 and U.S. patent application Ser. No. 654,821 which is expected to issue shortly. Such a fixture includes a base, a fluorescent lamp, and a panel with openings through which the light from the lamp diffuses. The base, lamp and panel are mounted together such that the lamp is between the base and diffuser panel. The base may have a nozzle through which a high velocity airstream is directed to flow parallel to the base and to emerge to the side of the fixture. This creates a venturi effect which sucks air through the fixture from the panel openings.
The panel may be in the form of a plurality of elongated cylindrical light-diffusing rods which are spaced from each other in the transverse direction. The rods may be transparent, translucent or reflective. Further, the panel may pivot from a closed position to an open position relative to the base to enable easy access to the lamp and/or ballast for service or replacement.
While such a fixture is suitable for use in moving vehicles, the assembly of the panel of cylindrical light diffusing rods is somewhat cumbersome. The use of transparent or translucent material for the rods means that the accumulation of any dust or film on them is readily noticeable.
Lighting fixtures which have open grills that are louvered and made of metal and other opaque materials have been used in offices, stores, schools, and other such facilities, as opposed to rail cars or other moving vehicles. Such open grill lamp fixtures help avoid the collection of insects and dirt because they are open. Cleaning, if needed, may be accomplished by a dusting brush.
It would be desirable to apply this open grill feature into a self-cleaning lighting fixture which promotes air mixing for effecting temperature equilibrium within an enclosure, such as a car of a public vehicle.